Helminthes and Diseases

• Helminthes belong to phylum Platyhelminthes & Nematoda (Nemathelminthes)

• Many parasitic groups (parasitic worms) are endoparasities of gut & blood in human body causing diseases (helminthiasis)

• 3-forms widespread

•Nematodiasis • Trematodiasis • Cestodiasis

• Diseases caused by nematode helminthes

• Highly prevalent disease caused by giant intestinal roundworms (Ascaris lumbricoides)

• Off-white in color resembling earthworm & most frequently seen in children

• Female longer than male

• Female lays 200,000 eggs daily passing out with human feces, remaining alive in soil for several days

• In man infection follows ingestion of embryonated eggs with contaminated food (raw vegetables, fruits) & drinking water

•Among children, playing in contaminated soil, there is also hand to mouth transfer of eggs

• In intestine, juveniles hatch out of eggs & cycle of larval development begins

• Juveniles penetrate the intestinal wall & migrate to liver & from there to heart & lungs

• Finally they return back into intestine & develop into adult parasites

• With adult Ascaris residing in intestine patient complains of abdominal pains, vomiting, headache, irritability, dizziness & night terrors

• Sometimes there is diarrhea & salivation

•Often patient grits his teeth in sleep

•When adult worms migrate through intestinal wall they cause severe peritonitis

•They may find their way into other areas causing appendicitis, gall bladder trouble & liver disease •In lungs, juveniles may cause bronchitis

• Treatment of human ascariasis has been fairly successful through oral administration of piperazine citrate syrup & Hexylresorcinol tablets

• Santonin & oil of Chenopodium are also useful

• Caused by 2-hookworms (Ancylostoma duodenale & Necator americanus)

• Both are parasites within intestine

• Most frequent in rural areas

• Female hookworms lay 5,000-10,000 eggs per day which pass out in stool

• Man acquires infection when eggs hatch & juveniles penetrate through soft skins of hands & feet

• They enter blood vessels & are carried to heart & lungs

• Now they make their way to one of the bronchial tubes, pass into small intestine & finally develop into adult worms

• Characteristic symptoms of the disease include gastro-intestinal disturbances, anemia & nervous disorders

• Patients appear pale & are often weak

• They complain of dizziness, ringing in ears & headache

• Nausea & vomiting are frequent

• In more severe cases, men may become impotent & women may cease to menstruate

• Safe drugs for treatment are tetrachloroethane & carbon tetrachloride

•Disease is caused by Enterobius vermicularis (pin or seatworms)

• Small white worms about 6-7 mm long

• Inhabiting upper part of colon

• Females migrate out through colon & rectum & deposit enormous number of eggs in skin folds about anus, where they cause intense itching

• When skin about anus is scratched eggs are easily picked upon fingers & under nails from where they find their way to food & are swallowed

• They hatch in stomach & juveniles migrate to colon & develop into adult worms

• Pinworm infection is more frequent in children than in adults

• Symptoms include severe itching around anus, loss of appetite, sleeplessness, bed-wetting, grinding of teeth, nausea & vomiting

• Piperazine is most effective drug in treatment

• Patient must wash his perianal region with warm water & soap before going to & rising from bed

• Disease is caused by Trichuris trichura (whipworm)

• Inhabits large intestine, mainly caecum or vermiform appendix

• Females lay enormous number of eggs daily passing through stool

• Eggs gain entry to human body with contaminated drinking water, raw water & vegetables

• They may also be spread by flies

• In intestine, eggs hatch & larvae develop into adult whipworms

• Patients suffering from whipworm disease complain of nausea, vomiting, constipation, headache, slight fever & paroxymal pains resembling appendicitis

• In more severe cases, anemia & eosinophilia develop

• Drugs used for expulsion are osarsol & dithiazanine

•Disease is caused by Trichinella spiralis

• Trichina worms & disease is widespread in America

• Transmitted by raw meat, especially pork

• Man becomes infected following ingestion of encysted larvae with raw or under-cooked pork

• In the intestine, larvae hatch out of cysts & develop into sexually mature adult worms

• Females lay eggs that hatch & resulting young larvae enter blood stream & carried to muscles of chest & legs

• Here they form cysts • Early symptoms of trichiosis are nausea, vomiting, edema of face & eyelids & fever

• After this muscular pains are felt

• Patient complains of pain in chewing, swallowing, breathing & moving his arms & legs

• No specific treatment

• Disease is caused by Strongyloides stercoralis (thread-worms)

• Invade lining of alimentary canal

• Females lay large number of eggs that pass out in feces & develop in to rhabditiform larvae

• These transform into filariform larvae penetrating skin of bare feet & thus, entering human body

• Patient with threadworm disease complains of nausea, dizziness & bloody diarrhea resulting from ulcerations due to parasites lodged within intestinal mucosa & glands

•There may also be vomiting, cough & fever •Most effective drug for treatment of thread worms is gentian violet •Dithiazamine also works well

• Causative organism for this disease is a nematode (Wuchereria bancrofti)

• Commonly known as filaria worm

• These tiny worms live in lymphatic system & connective tissues of body & are also found in circulating blood at night

• Infection is spread through Culex mosquito

• Following copulation, female worm delivers juveniles (Microfilariae)

• These at night get into blood capillaries of skin to be sucked up by mosquito with blood meal

• Mosquito transmits them into another human body where they enter the lymph nodes & develop into adult parasites

• Infection of filaria worms causes enlargement of limbs, scrotum & mammae

• Swelling occurs due to blockage of lymph circulation by parasitic worms, resulting into inflammation of lymph vessels & lymph glands

• No effective drug for eradication

• Cyanine dyes & diethylcarbamazine

• Very large swellings can sometimes be removed by surgery

•Diseases caused by trematode helminths

• Disease caused by Opisthorchis (Clonorchis) sinensis inhabiting bile ducts

• Disease is widespread in China, Japan, Korea, Vietnam & India

• Human infections are acquired through eating raw or undercooked fish harboring metacercariae

• Thousands of adult flukes are found in biliary ducts, causing thickening of duct walls

• Severe cases usually lead to cirrhosis & ultimate death

• Gentian violet & chloroquine proves helpful in curing infections

•Most important is prevention

•All freshwater fish should be thoroughly cooked before eating

• Disease is caused by intestinal fluke Fasciolopsis fuelleborni in India

• It utilizes snail as intermediate host in which it passes through an elaborate developmental cycle producing metacercariae that leave snail to be located on water plants

• Infections are acquired by eating these water plants particularly water nuts

• In intestine these metacercariae develop into adult worms within three months

• Worms cause erosion of intestinal lining resulting in bleeding & pain

•This is followed by diarrhea, nausea & vomiting •Hexylresorcinol & ‘Crystaloids’ anthelminthics are helpful in eradication of intestinal flukes

• Disease is caused by 3-species of blood flukes: S. mansoni, S. japonicum & S. haematobium

• These live in blood stream

• Disease is widespread throughout the world

• Females lay enormous number of eggs in blood stream from where find their way either into intestine (S. japonicum & S. mansoni) or urinary bladder (S. haematobium) & are ejected in feces or urine

• When eggs come in contact with water, miracidia hatch out & get into snail

• Here these develop into cercariae which leave snail, swim feely in water & penetrate skin of man

• Through blood circulation cercariae reach lungs to become adult worms

•Adults then get into blood stream

• Blood flukes cause asthmatic attacks & hepatitis

• This may be followed by fever, sweating, diarrhea, weight loss & lack of appetite

•Antimony compounds are recommended •Sanitary disposal of human feces & urine are essential for control

• Disease is caused by lung fluke (Paragonimus westermanii)

• Infection is widespread in Asia, Africa, South & Central America

• Flukes are found in lungs in encapsulated form

• Eggs are expelled out in sputum & when they come in contact with water these develop into miracidia

• Miracidia find their way into snail host where they develop into cercaria

• Cercariae merge & get into crabs & crayfish & encyst into metacercarial cyst

• Man acquires infection from eating raw or undercooked crabs & crayfish

• Encystment occurs in man’s intestine & juveniles migrate into lungs where they attain maturity & become encapsulated

• Lung flukes cause chronic cough with emission of bloody sputum

• Heavy infections cause chest pain with pleurisy, shortness of breath, fever & anemia

• Emetine hydrochloride & sulpha drugs are recommended for treatment of lung flukes

•Diseases caused by tapeworms

• Disease is caused by species belonging to Taenia which mainly include T. solium (pork tapeworm) & T. saginata (beef tapeworm)

• Man acquires infection by eating raw or undercooked pork or beef containing cysticerci

• In intestine cysticerci develop into adult tapeworms

• Presence of tapeworms in intestine cause gatrointestinal disorders

• Some patients complain of hunger pain

•Anemic conditions may also develpop •Atebrin or quinarcin hydrochloride is the drug of choice • Prevention requires eating of thoroughly cooked pork of beef

• Disease is cause by hydatid worm (Echinococcus granulosus)

• Primary host of this worm is dog in whose intestine eggs are set free

• These pass out in feces & develop into onchospheres

• Man acquires infection on eating food or drinking water contaminated with onchosphere containing eggs

• In man, hydatid cysts develop in liver, lungs & other tissues & represent the end of parasitic life-line

• Cysts cause inflammation of tissues

• Presence of cysts in brain & kidney may prove fatal

•Atebrin or quinacrine hydrochloride is the drug of choice

• Nematodes are elongated, unsegmented, triploblastic, pseudocoelomate animals commonly known as ‘roundworms’

• They are widely distributed free-living as well as parasitic animals

• Free nematodes are found in all sorts of environments in sea, in freshwater & in soil on land

• Parasitic nematodes parasitize all kinds of plants & animals & display all degrees of parasitism

• About 50 species of nematodes are known to occur in man but only a dozen of these are of pathogenic importance

• They are of utmost economic & medical importance to man

• These are Trichuris trichura, Trichinella spiralis, Rhabditis, Enterobius vermicularis, Dracunculus mediensis, Loa loa, Toxocara canis, Ancylostoma duodenale, Necator americanus, Wuchereria bancrofti & Ascaris lumbricoides